[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) › Cetirizine # Cetirizine ## H1 antihistamines? H1 antihistamines A second-generation antihistamine for hay fever and hives; it acts fast and is the most likely of its group to cause some drowsiness. Updated Nov 1, 2026 ## Quick facts **Group** [H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) **Target** Histamine H1 receptor **Used for** Allergic rhinitis · Urticaria **Key effects** Drowsiness and tiredness · Dry mouth · Headache **Monitor** Symptom relief · Drowsiness **ATC** R06AE07 No doses: the clinician sets them by the current guideline. On this page - The basics Mechanism of action - Indications - Adverse effects - Pharmacokinetics - Memory aid - Safety Contraindications - Key interactions - What is monitored - Administration and safety - Pregnancy and breastfeeding - Nursing care - Study Test yourself - Connections Connections ## Mechanism of action ◎**Histamine H1 receptor**Cetirizine ⓘ The figure shows desloratadine bound to the human histamine H1 receptor (cryo-electron microscopy); cetirizine binds the same site. **Target in 3D:** Histamine H1 receptor. PDB structure 8X64 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8X64) · Drag to rotate · pinch to zoom Cetirizine is the carboxylic-acid metabolite of hydroxyzine. As a selective peripheral H1 inverse agonist it blocks histamine effects on nerves, vessels and glands of the nose, eyes and skin. It penetrates the brain more than loratadine or fexofenadine, which explains why a minority of patients feel drowsy. - Cetirizine binds peripheral H1 receptors - The receptors stay in their inactive form - Histamine itch, sneezing and wheals are blocked - A little enters the brain: some people feel drowsy ## Indications - Allergic rhinitis [Allergic rhinitis →](https://durgical.com/en/conditions/allergic-rhinitis/) - Urticaria (hives) [Urticaria and angioedema →](https://durgical.com/en/conditions/urticaria-and-angioedema/) - Itch of allergic skin conditions such as atopic eczema [Atopic dermatitis →](https://durgical.com/en/conditions/atopic-dermatitis/) ## Adverse effects ### Common - Drowsiness and tiredness - Dry mouth - Headache - Sore throat ### Serious (rare, important) - Allergic reaction to the drug: rare ## Contraindications - Hypersensitivity to cetirizine, levocetirizine or hydroxyzine - Caution and lower exposure in kidney disease ## Key interactions **Alcohol, benzodiazepines, opioids and other CNS depressants** Additive sedation and slowed breathing ## What is monitored - Symptom relief - Drowsiness - Kidney function in older adults ## Administration and safety - Oral tablets, chewable tablets or syrup; with or without food - Eye-drop and injectable forms exist in some countries - Levocetirizine is its active enantiomer, not a different drug: they are not combined ## Pregnancy and breastfeeding Cetirizine has a large body of pregnancy experience without a clear signal of harm; use is decided with the clinician. ## Nursing care - Teach not to drive or operate machinery until the effect is known, and to avoid alcohol - Check kidney function in older or renally impaired patients - Ask about previous reactions to hydroxyzine (cross-sensitivity) ## Pharmacokinetics **Absorption** Rapidly absorbed by mouth **Metabolism** Very little metabolism **Elimination** Mostly unchanged in the urine, so it builds up in kidney failure **Onset and duration** Within about an hour, lasting about a day ## Memory aid CETirizine = the Child of hydroxyzine (its metabolite) that still naps a little. ## Test yourself Think of the answer, then tap the question to see it. ## Which first-generation antihistamine is cetirizine derived from? Hydroxyzine; cetirizine is its metabolite. ## Among second-generation antihistamines, which is most likely to cause drowsiness? Cetirizine. ## Why does cetirizine accumulate in kidney failure? It is excreted largely unchanged in the urine. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/cetirizine/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## Connections ## Related drugs 3 - [Hydroxyzine](https://durgical.com/en/pharmacology/hydroxyzine/) - [Loratadine](https://durgical.com/en/pharmacology/loratadine/) - [Fexofenadine](https://durgical.com/en/pharmacology/fexofenadine/) ## Related conditions 3 - [Allergic rhinitis](https://durgical.com/en/conditions/allergic-rhinitis/) - [Urticaria and angioedema](https://durgical.com/en/conditions/urticaria-and-angioedema/) - [Atopic dermatitis](https://durgical.com/en/conditions/atopic-dermatitis/) [← Back to the class: H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [Cetirizine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a623043.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [Cetirizine: antihistamine that relieves allergy symptoms - NHS](https://www.nhs.uk/medicines/cetirizine/) (NHS, 2026); [DailyMed - HYDROXYZINE HYDROCHLORIDE tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d73a8d3c-66ed-40af-9f1d-b710672a34fb) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=R06AE07) (WHO Collaborating Centre for Drug Statistics Methodology, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/cetirizine/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/cetirizine/